UC Berkeley study finds Earth’s core grows asymmetrically

Infographic depicting UC Berkeley seismologists' discovery that Earth's core grows asymmetrically
Amber Chia/Staff

Related Posts

A study published Thursday co-authored by three UC Berkeley researchers found that the Earth’s core grows asymmetrically.

Campus researchers Daniel Frost and Brian Chandler and professor Barbara Romanowicz, joined by Marine Lasbleis from the Université de Nantes, discovered that the Earth’s solid inner core grows faster on its eastern side than its western side, according to a UC Berkeley press release. The research project was given $152,142 from a National Science Foundation geophysics grant, according to Frost, the assistant project scientist. 

“The Earth’s core has two parts; it has the liquid iron outer core and the solid iron inner core,” Frost said. “As the Earth cools through time, the liquid iron outer core is freezing, solidifying and that grows the inner core.”

Studies from 30 to 40 years ago have shown that seismic waves travel faster from north to south than they do from east to west, Frost added. The current study sought to answer why.

According to the press release and Frost, all studies used data obtained from seismometers, or machines that measure seismic activity such as earthquakes, placed around the planet.

The researchers first created a model which could simulate different versions of the Earth’s core. They then adjusted the model to fit the data from the seismometers and found that the one that best fit the data had an inner core growing faster on the eastern side than the west, according to Frost.

“We varied a few parameters just to try to get the match,” Frost said. “We weren’t approaching this from the direction of knowing how the inner core grows. It’s more a case of asking the question — how does the inner core grow? The only constraint we have on that is the seismology.”

The asymmetrical growth of the inner core has significant implications for how the planet’s magnetic field works, Frost added. The magnetic field, which we use for navigation and protects life on Earth from too much sun, is generated by the movement of liquid iron in the outer core.

Frost said he speculates that the reason for the inner core’s asymmetrical growth is that some unknown force is cooling the planet’s eastern side faster than its western side. Frost added that one potential source could be the increased subduction in the eastern hemisphere, which takes cold parts of the crust and places them near the crust-mantle boundary.

While the researchers have not yet found how the inner core’s growth affects the flow of the outer core, Frost said he has recently obtained more funding from the National Science Foundation to continue his research.

“You’re never done. There’s always another question to be asked,” Frost said. “(We’ll be) actually testing with real materials how the inner core can move.”

Contact Christopher Ying at [email protected], and follow him on Twitter at @ChrisYingg.